Plate material and manufacturing method thereof

ABSTRACT

A plate material includes a substrate and a coating. The substrate is a plate-like member that does not have protrusions and depressions of submicron order oriented in the thickness direction thereof. The coating is formed on the surface of the substrate with a paint-like material having affinity with respect to the substrate.

CROSS REFERENCE TO RELATED APPLICATIONS

This U.S. national stage application claims priority under 35 U.S.C.§119(a) to Japanese Patent Application No. 2003-350585, filed in Japanon Oct. 9, 2003, the entire contents of which are hereby incorporated byreference.

TECHNICAL FIELD

The present invention relates to a plate material and a manufacturingmethod thereof.

BACKGROUND OF THE INVENTION

The outdoor units and indoor units of air conditioning systems aregenerally provided with heat exchangers for exchanging heat with theoutside air. The heat exchangers are normally provided with a pluralityof heat radiating fins, a plurality of heat exchanger tubes, and apropeller or other blowing means. The plurality of heat radiating finsare plate-like members arranged with a prescribed spacing there-betweenalong the thickness direction thereof. The plurality of heat exchangertubes are arranged so as to pass through the plurality of heat radiatingfins in the thickness direction of the heat radiating fins. The blowingmeans serves to deliver a flow of air over the plurality of heatradiating fins and heat exchanger tubes.

In such a heat exchanger, the air blown into the gaps between adjacentheat radiating fins by the blowing means causes heat to be exchanged andthe refrigerant flowing inside the heat exchanger tubes eitherevaporates or condenses.

The heat radiating fins generally comprise a plate material that hasbeen worked into a prescribed fin shape using a die. The plate materialis constructed from a plate-like substrate made of pure aluminum or analuminum alloy and a coating that is formed on the surface of thesubstrate. Normally, the substrate is made by rolling the aluminum oraluminum alloy into a plate-like form using rolling oil and, thus, oilexists on the surface of the substrate.

Consequently, conventionally, when a coating is to be formed on thesurface of the substrate, an oil removal treatment is first applied tothe substrate and then a coating method like one of the following (forexample) is used to form the coating:

(1) A chromic acid treatment is applied to form a chromate coating and ahydrophilic coating is formed over the chromate coating. (See, forexample, Japanese Publication No. 62-105629.)

(2) A hydrophilic paint-like material is applied to form the coating.(See, for example, Japanese Publication No. 63-303729.)

(3) A phosphoric acid treatment, an alkaline treatment, etching, orother surface roughening treatment is applied to the substrate and thena corrosion resistant coating is formed on the substrate. (See, forexample, Japanese Publication No. 2003-171774.)

With the method (3), a fine roughness (protrusions and depressions) ofsubmicron order is formed on the surface of the substrate.

With the method (1), the equipment cost is large because it is necessaryto use a prescribed treatment layer and the running cost is high becauseharmful waste liquid is discharged from the process and must be treated.Thus, it seems reasonable to omit the chromic acid treatment and selecta method such as method (2) in which a paint-like material is applieddirectly to the substrate using a paint application method. However,when the paint-like material is applied directly, the adhesion betweenthe substrate and the coating is poor and a sufficiently durable platematerial cannot be obtained. Meanwhile, when the method (3) is adopted,specific treatment equipment is required and the cost is high.

Also, all of the methods (1) to (3) require the substrate to be treatedin advance to remove oil and when a roughening treatment is applied, thenumber of processing steps required to manufacture the plate materialincreases and causes the cost to increase.

In the case of a conventional plate material made by applying a chromicacid treatment to the substrate so as to form a chromate coating on thesurface of the substrate, the chromate coating improves the corrosionresistance of the plate material. However, since a chromate coating doesnot have sufficient hydrophilicity, it has poor water wettingcharacteristic when used as is on a heat radiating fin. As a result,water droplets stuck on the surface of the fin cause such problems asincreased air flow resistance.

In view of these issues, technologies have been proposed in which achromate coating or water soluble resin coating is applied to thesurface of the substrate as a corrosion resistant coating and ahydrophilic coating is applied on top of the corrosion resistant coatingin order to ensure sufficient degrees of both corrosion resistance andhydrophilicity. (See, for example, Japanese Publication No. 62-105629.)With the technology described in Japanese Publication No. 62-105629, aplate material having sufficient degrees of both corrosion resistanceand hydrophilicity can be obtained. Particularly when a water solubleresin is used for the corrosion resistant coating, the treatment layerrequired for a chromic acid treatment is not necessary and thetechonology is thus advantageous in terms of production costs andenvironmental concerns.

SUMMARY OF THE INVENTION

However, with the conventional technology described above, since a watersoluble resin containing a hydrophilic group is used in order to ensurethat the corrosion resistant coating adheres to the substrate, thecorrosion resistant coating is eroded (washed away) by adhered water andmoisture that penetrates the corrosion resistant coating causes thesubstrate to corrode. As a result, the durability of the plate materialdeclines.

The object of the present invention is to improve the adhesion betweenthe coating and the substrate and to reduce the cost required to producethe plate material.

Another object of the present invention is to provide a plate materialhaving both corrosion resistant and hydrophilic properties, as well asimproved durability.

A plate material in accordance with a first aspect of the presentinvention is provided with a substrate and a coating. The substrate is aplate-like member that does not have protrusions and depressions ofsubmicron order oriented in the thickness direction thereof. The coatingis formed on the surface of the substrate and made of a paint-likematerial having affinity with respect to the substrate.

In the description of the present invention, “submicron-orderprotrusions and depressions oriented in the thickness direction of thesubstrate” are protrusions and depressions in the range of sizes equalto or larger than 0.1 μm and smaller than 1.0 μm and are formed on, forexample, a rolled plate-like substrate by means of an alkalinetreatment, etching treatment, or other roughening treatment. Also, a“paint-like material having affinity with respect to the substrate” is apaint-like material having good adhesion with respect to the substratewhen it is in the form of a coating. More specifically, as will bedescribed later, it is a paint-like material containing a specificalcohol-based solvent.

With this plate material, the substrate does not have submicron orderprotrusions and depressions on its surface and thus has not beensubjected to a roughening treatment. However, the coating has excellentadhesion with respect to such a substrate because it is made of apaint-like material having affinity with respect to the substrate. Sincethis plate material can be obtained without applying a rougheningtreatment, the production cost is reduced.

A plate material in accordance with a second aspect of the presentinvention is a plate material in accordance with the first aspect,wherein the paint-like material is a hydrophobic organic paint-likematerial.

Due to its coating being made of a hydrophobic organic paint-likematerial, this plate material has excellent corrosion resistance and iswell suited for use as heat radiating fins of a heat exchanger.

A plate material in accordance with a third aspect of the presentinvention is a plate material in accordance with the first or secondaspect, wherein the surface tension of the paint-like material is equalto or larger than 25 and less than or equal to 35 dyn/cm.

Since the surface tension of the paint-like material is comparativelysmall, the paint-like material has good wetting capacity with respect tothe surface of the substrate when it is applied, even though thesubstrate has not been subjected to a roughening treatment. As a result,the paint-like material has good adhesion with respect to the substratewhen it is in the form of a coating.

A plate material in accordance with a fourth aspect of the presentinvention is a plate material in accordance with any one of the firstthrough third aspects, wherein the paint-like material contains analcohol-based solvent at a content of 1 to 10 wt %. In this invention,the content of the alcohol-based solvent is expressed as a percentage ofthe total weight of paint-like material (wt %), i.e., the weight ofalcohol-based solvent contained in 100 weight units of paint-likematerial.

With this plate material, the alcohol-based solvent reduces the surfacetension of the paint-like material and thereby improves the adhesionbetween the coating and the substrate.

A plate material in accordance with a fifth aspect of the presentinvention is a plate material in accordance with any one of the firstthrough third aspects, wherein the paint-like material contains analcohol-based solvent at a content of 1 to 5 wt %.

With this plate material, the adhesion between the substrate and thecoating is improved in a more effective manner because the alcohol-basedsolvent content is in the aforementioned range (1 to 5 wt %).

A plate material in accordance with a sixth aspect of the presentinvention is a plate material in accordance with the fourth or fifthaspect, wherein the alcohol-based solvent is made substantially of analcohol having four or more carbon atoms.

With this plate material, the adhesion between the substrate and thecoating is improved in an effective manner because the alcohol-basedsolvent is made of an alcohol having four or more carbon atoms.

A plate material in accordance with a seventh aspect of the presentinvention is a plate material in accordance with any one of the firstthrough sixth aspects, wherein the viscosity of the paint-like materialis equal to or larger than 5 pa-s and less than or equal to 20 pa-s.

Since the viscosity of the paint-like material is comparatively small,the paint-like material has good wetting capacity with respect to thesurface of the substrate where it is applied—even though the substratehas not been subjected to a roughening treatment. As a result, thepaint-like material has good adhesion with respect to the substrate whenit is in the form of a coating.

A plate material in accordance with an eighth aspect of the presentinvention is a plate material in accordance with any one of the firstthrough seventh aspects, wherein the coating is a corrosion resistantcoating that is formed with a corrosion resistant paint-like materialand made of a hydrophobic organic compound. Additionally, in this platematerial, a hydrophilic coating made of a hydrophilic paint-likematerial is provided on the surface of the corrosion resistant coating.

With this plate material, the adhesion between the substrate and thecoating is improved and the cost required to produce the plate materialis reduced. Furthermore, since the corrosion resistant coating is madeof a hydrophobic organic compound and does not contain a hydrophilicgroup, erosion of the corrosion resistant coating by adhered water issuppressed in comparison with a corrosion resistant coating made of awater soluble resin and moisture can be prevented from penetrating thecorrosion resistant coating and causing the substrate to corrode.

A plate material in accordance with a ninth aspect of the presentinvention is a plate material in accordance with the eighth aspect,wherein the hydrophilic paint-like material contains a volatile organicsolvent.

Although it is normally difficult to form a hydrophilic coating on thesurface of a corrosion resistant coating made of a hydrophobic organiccompound, research conducted by the inventors has shown that ahydrophilic coating can be formed on the surface of such a corrosionresistant coating by using a hydrophilic paint-like material to which anorganic solvent has been added. With this plate material, two coatingshaving different properties can be formed on top of each other with asimple method.

A plate material in accordance with a tenth aspect of the presentinvention is a plate material in accordance with the eighth or ninthaspect, wherein the corrosion resistant coating is formed on the surfaceof a substrate that has not been subjected to a chromic acid treatment.

With this plate material, the corrosion resistant coating is made of ahydrophobic organic compound, which has superior durability to a coatingmade of a water soluble resin. Consequently, the decline in durabilitythat would otherwise result from the omission of the chromate coatingcan be suppressed. Also, with this plate material, the production costcan be reduced and there is no discharge of harmful waste liquidsbecause the chromic acid treatment is not necessary.

A plate material in accordance with an eleventh aspect of the presentinvention is a plate material in accordance with any one of the eighththrough tenth aspects, wherein the corrosion resistant coating is formedon the surface of a substrate that has not been subjected to an oilremoval treatment.

With this plate material, the pre-treatment steps executed with respectto the substrate during manufacturing can be reduced because the oilremoval treatment is omitted.

A plate material in accordance with a twelfth aspect of the presentinvention is a plate material in accordance with any one of the firstthrough eleventh aspects, wherein the substrate is made of pure aluminumor an aluminum alloy.

Aluminum substrates are often manufactured with a rolling process inwhich rolling oil is used. With this plate material, by using apaint-like material having affinity with respect to the substrate, acoating can be formed on such an aluminum substrate without applying anoil removal treatment.

A plate material in accordance with a thirteenth aspect of the presentinvention is a plate material in accordance with any one of the firstthrough twelfth aspects, wherein the plate material is used as a heatradiating fin of a heat exchanger.

With this plate material, the adhesion between the substrate and thecoating is good and the plate material has excellent durability. Thus,the plate material is well suited for such an application.

A plate material manufacturing method in accordance with a fourteenthaspect of the present invention is provided with a first step and asecond step. In the first step, a plate-like substrate that does nothave protrusions and depressions of submicron order oriented in thethickness direction thereof on its surface is prepared. In the secondstep, a coating is formed on the surface of the substrate with apaint-like material having affinity with respect to the substrate.

Research conducted by the present inventor and others has shown that acoating can be formed on the surface of a substrate without subjectingthe substrate to an oil removal treatment or a roughening treatment ifthe coating is made of a paint-like material having affinity withrespect to the substrate and is applied directly. Said researchdemonstrates that when the plate material is made using such a method,excellent adhesion is obtained between the coating and the substrate.Furthermore, by using said method, a plate material having excellentdurability is obtained and the production cost can be reduced becausesuch surface treatments as oil removal treatments and rougheningtreatments can be omitted.

A plate material manufacturing method in accordance with a fifteenthaspect of the present invention is a manufacturing method in accordancewith the fourteenth aspect, wherein the paint-like material is ahydrophobic organic paint-like material.

With this manufacturing method, a plate material having excellentcorrosion resistance can be obtained because the coating formed on thesurface of the substrate is made of a hydrophobic organic paint-likematerial.

A plate material manufacturing method in accordance with a sixteenthaspect of the present invention is a manufacturing method in accordancewith the fourteenth or fifteenth aspect, wherein the paint-like materialhas a surface tension of 25 dyn/cm to 35 dyn/cm.

With this manufacturing method, since the surface tension of thepaint-like material is comparatively small, the paint-like material hasgood attraction with respect to the surface of the substrate even if thesubstrate has not been subjected to a roughening treatment. As a result,a plate material having excellent adhesion between the coating and thesubstrate can be obtained. Also, with this manufacturing method, theproduction cost of the plate material can be reduced because the oilremoval treatment and roughening treatment can be omitted.

A plate material manufacturing method in accordance with a seventeenthaspect of the present invention is a manufacturing method in accordancewith any one of the fourteenth through sixteenth aspects, wherein thepaint-like material contains an alcohol-based solvent at a content of 1to 10 wt %.

Research conducted by the inventor specifically demonstrates that whenan alcohol-based solvent is added to the paint-like material at theaforementioned content (weight percentage), the paint-like material hasgood attraction with respect to the substrate—even though the substratehas not been subjected to a roughening treatment—and thus the adhesionbetween the coating and the substrate is improved. By using thismanufacturing method, a plate material having excellent durability canbe obtained.

A plate material manufacturing method in accordance with an eighteenthaspect of the present invention is a manufacturing method in accordancewith any one of the fourteenth through sixteenth aspects, wherein thepaint-like material contains an alcohol-based solvent at a content of 1to 5 wt %.

With this manufacturing method, the adhesion between the substrate andthe coating can be improved in a more effective manner because thealcohol-based solvent content in the paint-like material is in theaforementioned range (1 to 5 wt %).

A plate material manufacturing method in accordance with a nineteenthaspect of the present invention is a plate material in accordance withthe seventeenth or eighteenth aspect, wherein the alcohol-based solventis made substantially of an alcohol having four or more carbon atoms.

With this manufacturing method, since a paint-like material containingan alcohol-based solvent having the aforementioned feature is used, thepaint-like material has good attraction with respect to the surface ofthe substrate even though the substrate has not been subjected to aroughening treatment. As a result, a plate material having excellentadhesion between the coating and the substrate can be obtained.

A plate material manufacturing method in accordance with a twentiethaspect of the present invention is a plate material in accordance withany one of the fourteenth through nineteenth aspects, wherein theviscosity of the paint-like material is equal to or larger than 5 pa-sand less than or equal to 20 pa-s.

With this manufacturing method, since the viscosity of the paint-likematerial is comparatively small, the paint-like material has goodattraction with respect to the surface of the substrate even though thesubstrate has not been subjected to a roughening treatment. As a result,a plate material having excellent adhesion between the coating and thesubstrate can be obtained.

A plate material manufacturing method in accordance with a twenty-firstaspect of the present invention is a manufacturing method in accordancewith any one of the fourteenth through twentieth aspects, wherein in thesecond step, a corrosion resistant coating made of a hydrophobic organiccompound is formed on the surface of the plate-like substrate byapplying a corrosion resistant paint-like material. Additionally, thismanufacturing method includes a third step in which a hydrophiliccoating is formed on the surface of the corrosion resistant coating byapplying a hydrophilic paint-like material.

With this manufacturing method, the adhesion between the substrate andthe coating is improved and the cost required to produce the platematerial is reduced. Furthermore, since the corrosion resistant coatingis made of a hydrophobic organic compound, erosion of the corrosionresistant coating by adhered water is suppressed and moisture can beprevented from penetrating the corrosion resistant coating and causingthe substrate to corrode.

A plate material manufacturing method in accordance with a twenty-secondaspect of the present invention is a manufacturing method in accordancewith the twenty-first aspect, wherein in the third step, the hydrophilicpaint-like material containing a volatile organic solvent is applied.

With this manufacturing method, the organic solvent contained in thehydrophilic paint-like material enables a hydrophilic coating to beformed easily on the surface of a hydrophobic corrosion resistantcoating. Thus, two coatings having different properties can be formed ontop of each other with a simple method.

A plate material manufacturing method in accordance with a twenty-thirdaspect of the present invention is a manufacturing method in accordancewith the twenty-first or twenty-second aspect, wherein in the secondstep, the corrosion resistant painte-like material is applied on thesubstrate that has not been subjected to a chromic acid treatment.

With this manufacturing method, since the corrosion resistant coating ismade of a hydrophobic organic compound, the corrosion resistant coatingcan be formed satisfactorily on the surface of the substrate even thougha chromate coating is not formed. Furthermore, since the corrosionresistant coating is made of a hydrophobic organic compound, the declinein durability that would otherwise result from the omission of thechromate coating is suppressed. Also, with this manufacturing method,the production cost can be reduced and there is no discharge of harmfulwaste liquids because the chromic acid treatment is not necessary.

A plate material manufacturing method in accordance with a twenty-fourthaspect of the present invention is a manufacturing method in accordancewith the twenty-first or twenty-third aspect, wherein in the secondstep, the corrosion resistant paint-like material is applied on thesubstrate that has not been subjected to an oil removal treatment.

With this manufacturing method, the pre-treatment steps executed withrespect to the substrate during manufacturing can be reduced because theoil removal treatment is omitted.

A plate material manufacturing method in accordance with a twenty-fifthaspect of the present invention is a manufacturing method in accordancewith any one of the fourteenth through twenty-fourth aspects, whereinthe substrate is made of pure aluminum or an aluminum alloy.

With this manufacturing method, the adhesion of the coating can beimproved even with respect to the substrate that is often rolled using arolling oil.

A plate material manufacturing method in accordance with a twenty-sixthaspect of the present invention is a manufacturing method in accordancewith any one of the fourteenth through twenty-fifth aspects, wherein theplate material is used as a heat radiating fin of a heat exchanger.

With manufacturing method, the adhesion between the substrate and thecoating is good and a plate material having excellent durability isobtained. Thus, the plate material is well suited for such anapplication.

With the first aspect, excellent adhesion is achieved between thecoating and the substrate even when the substrate has not been roughenedbecause the coating is made with paint-like material having affinitywith respect to the substrate. Since this plate material can be obtainedwithout applying a roughening treatment, the production cost is reduced.

With the second aspect, the corrosion resistance is excellent and thusthe plate material is well suited for use as, for example, a heatradiating fin of a heat exchanger.

With the third aspect, the paint-like material has good attraction withrespect to the surface of the substrate even if the substrate has notbeen subjected to a roughening treatment and, thus, the paint-likematerial has good adhesion with respect to the substrate when it is inthe form of a coating.

With the fourth aspect, the adhesion between the coating and thesubstrate is improved.

With the fifth aspect, the adhesion between the coating and thesubstrate is improved even more effectively.

With the sixth aspect, the adhesion between the coating and thesubstrate is improved even more effectively.

With the seventh aspect, the paint-like material has good attractionwith respect to the surface of the substrate even if the substrate hasnot been subjected to a roughening treatment and, thus, the paint-likematerial has good adhesion with respect to the substrate when it is inthe form of a coating.

With the eighth aspect, the adhesion between the substrate and thecoating is improved and the cost required to produce the plate materialis reduced. Furthermore, since the corrosion resistant coating is madeof a hydrophobic organic compound and does not contain a hydrophilicgroup, erosion of the corrosion resistant coating by adhered water issuppressed in comparison with a corrosion resistant coating made of awater soluble resin and moisture can be prevented from penetrating thecorrosion resistant coating and causing the substrate to corrode.

With the ninth aspect, two coatings having different properties can beformed on top of each other with a simple method.

With the tenth aspect, the decline in durability that would otherwiseresult from the omission of the chromate coating can be suppressed.Also, the production cost can be reduced and there is no discharge ofharmful waste liquids because the chromic acid treatment is notnecessary.

With the eleventh aspect, the corrosion resistant coating is made of ahydrophobic organic compound, which has superior durability to a coatingmade of a water soluble resin. Consequently, the decline in durabilitythat would otherwise result from the omission of the chromate coatingcan be suppressed. Also, with this plate material, the production costcan be reduced and there is no discharge of harmful waste liquidsbecause the chromic acid treatment is not necessary.

Aluminium substrates are often manufactured with a rolling process inwhich rolling oil is used. With the twelfth aspect, by using apaint-like material having affinity with respect to the substrate, acoating can be formed on such an aluminium substrate without applying anoil removal treatment.

With the thirteenth aspect, the adhesion between the substrate and thecoating is good and the plate material has excellent durability. Thus,the plate material is well suited for use as a heat radiating fin for aheat exchanger.

With the fourteenth aspect, a plate material having excellent durabilityis obtained and the production cost can be reduced because such surfacetreatments as oil removal treatments and roughening treatments can beomitted.

With the fifteenth aspect, a plate material having excellent corrosionresistance can be obtained because the coating formed on the surface ofthe substrate is made of a hydrophobic organic paint-like material.

With the sixteenth aspect, the paint-like material has good attractionwith respect to the surface of the substrate even if the substrate hasnot been subjected to a roughening treatment and, thus, a plate materialhaving excellent adhesion between the coating and the substrate can beobtained. Also, the production cost of the plate material can be reducedbecause the oil removal treatment and roughening treatment can beomitted.

With the seventeenth aspect, a plate material having excellentdurability can be obtained.

With the eighteenth aspect, the adhesion between the coating and thesubstrate of the plate material is improved even more effectively.

With the nineteenth aspect, the paint-like material has good attractionwith respect to the surface of the substrate even if the substrate hasnot been subjected to a roughening treatment and, as a result, a platematerial having excellent adhesion between the coating and the substratecan be obtained.

With the twentieth aspect, the paint-like material has good attractionwith respect to the surface of the substrate even if the substrate hasnot been subjected to a roughening treatment and, thus, a plate materialhaving excellent adhesion between the coating and the substrate can beobtained.

With the twenty-first aspect, the adhesion between the substrate and thecoating is improved and the cost required to produce the plate materialis reduced. Furthermore, since the corrosion resistant coating is madeof a hydrophobic organic compound, erosion of the corrosion resistantcoating by adhered water is suppressed and moisture can be preventedfrom penetrating the corrosion resistant coating and causing thesubstrate to corrode.

With the twenty-second aspect, two coatings having different propertiescan be formed on top of each other with a simple method.

With the twenty-third aspect, since the corrosion resistant coating ismade of a hydrophobic organic compound, the corrosion resistant coatingcan be formed satisfactorily on the surface of the substrate even thougha chromate coating is not formed. Furthermore, since the corrosionresistant coating is made of a hydrophobic organic compound, the declinein durability that would otherwise result from the omission of thechromate coating is suppressed. Also, with this manufacturing method,the production cost can be reduced and there is no discharge of harmfulwaste liquids because the chromic acid treatment is not necessary.

With the twenty-fourth aspect, the pre-treatment steps executed withrespect to the substrate during manufacturing can be reduced because theoil removal treatment is omitted.

With the twenty-fifth aspect, the adhesion of the coating can beimproved even with respect to the substrate that is often rolled using arolling oil.

With the twenty-sixth aspect, the adhesion between the substrate and thecoating is good and a plate material having excellent durability isobtained. Thus, the plate material is well suited for the aforementionedapplication.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical cross sectional view of a plate material thatemploys an embodiment of the present invention.

FIG. 2 is a top plan view of a heat exchanger heat radiating fin made ofthe plate material.

FIG. 3 is a vertical cross sectional view of the same heat radiatingfin.

DESCRIPTION OF THE INVENTION

FIG. 1 shows a plate material that employs an embodiment of the presentinvention.

Although the plate material 1 described herein is preferred for use as aheat radiating fin for a heat exchanger, the plate material 1 of thepresent invention can be used for applications other than a heatradiating fin 11 for a heat exchanger (see FIGS. 2 and 3). The inventionis not limited in any particular way to the constituent featuresdescribed below.

The plate material 1 includes a substrate 3, a corrosion resistantcoating 5, and a hydrophilic coating 7.

The substrate 3 is a plate-like member made of pure aluminium or analuminium alloy. Examples of aluminium allows that can be used includeAl—Cu alloys, Al—Mg alloys, and Al—Mg—Si alloys. The substrate 3 made byrolling the aluminium or aluminium alloy using a rolling oil and rollingoil remains on the surface thereof.

The substrate 3 in this embodiment is worked into a plate-like form byrolling the aluminium or aluminium alloy using a rolling oil. Thesubstrate 3 does not have protrusions and depressions of submicron orderoriented in the thickness direction thereof, i.e., does not have finescratches formed by a surface roughening treatment or other surfacetreatment. Furthermore, the substrate 3 may have protrusions anddepressions of larger than submicron order formed by contact with therollers during rolling.

The thickness of the substrate 3 is preferably in the range of 80 to 150μm or, even more preferably, in the range of 90 to 120 μm. A thicknessof 115 μm is particularly preferred.

The corrosion resistant coating 5 is formed on the surface of thesubstrate 3 with a paint-like material (which can include a corrosiveresistant paint-like material) that has affinity with respect to thesubstrate 3 and is made of a hydrophobic organic compound. As will bedescribed later, the corrosion resistant coating 5 is formed in acorrosion resistant coating forming step in which a paint-like material(which can include a corrosive resistant paint-like material) that hasaffinity with respect to the substrate 3 and is applied to the surfaceof the substrate 3 and dried. Here, a coating made of a hydrophobicorganic compound means that the coating does not contain any hydrophilicgroups. More specifically, when the coating is analysed with an infraredspectrometer, peaks resulting from such hydrophilic groups as hydroxygroups and carboxyl groups are substantially not detected in theinfrared spectrum.

The paint-like material having affinity with respect to the substrate isa hydrophobic organic paint-like material and contains a coating filmforming component, additives, a solvent, and a pigment. The coating filmforming component is preferably a dual component resin, such asacrylic-melamine resin, urethane-phenol resin, or zirconiumfluoride-acrylic resin, because such dual component resins have superiorcorrosion resistance compared to the epoxy resins conventionally usedfor corrosion resistant coatings. Examples of additives includeplasticizers, hardeners, pigment dispersing agents, and emulsifyingagents.

For reasons related to the paint-like material drying characteristicsand the resin solubility, it is preferable for the solvent to be analcohol-based solvent made substantially of an alcohol having four ormore carbon atoms, such as butanol and hexanol. For reasons related tothe resin solubility, it is preferable for the solvent content in thepaint-like material to be at least 1 wt % (i.e., 1 weight unit ofsolvent per 100 weight units of paint-like material) and still morepreferable for the solvent content to be at least 3 wt %. Meanwhile, forreasons related to flammability, it is preferable for the solventcontent not to exceed 10 wt % and still more preferable for the solventcontent not to exceed 5 wt %. For reasons related to liquid repellency,it is preferable for the surface tension of the hydrophobic organicpaint-like material to be at least 5 dyn/cm and still more preferablefor the surface tension to be at least 25 dyn/cm. Meanwhile, for reasonsrelated to penetration into the protrusions and depressions of thesurface, it is preferable for the surface tension not to exceed 50dyn/cm and still more preferable for the surface tension not to exceed35 dyn/cm.

The thickness of the corrosion resistant coating 5 is preferably in therange of 0.5 to 3.0 μm and still more preferably in the range of 1 to1.5 μm. A thickness of 1.0 μm is particularly preferred.

The hydrophilic coating 7 is a coating formed on the surface of thecorrosion resistant coating 5 and is made of a hydrophilic paint-likematerial. As will be described later, the hydrophilic coating 7 is madein a hydrophilic coating forming step in which a corrosive resistantpaint-like material is applied to the surface of the corrosion resistantcoating 5 and dried. The hydrophilic paint-like material contains acoating film forming component, additives, a solvent, and a pigment.Specifically, the coating film forming component is preferably apolyethylene glycol resin, a polyvinyl alcohol acrylic resin, or acellulose acrylic resin.

The thickness of the corrosion resistant coating 7 is preferably in therange of 0.1 to 1.0 μm and still more preferably in the range of 0.3 to0.5 μm. A thickness of 0.3 μm is particularly preferred.

The method of manufacturing the plate material will now be described.

The manufacturing method includes a substrate preparation step, acorrosion resistant coating forming step, and a hydrophilic coatingforming step.

In the substrate preparation step, a plate-like substrate that does nothave protrusions and depressions of submicron order or larger orientedin the thickness direction thereof on its surface is prepared. Thesubstrate 3 prepared in this step has been made by rolling a substratematerial into a plate-like form using rolling oil and rolling oilremains on the surface thereof.

In the corrosion resistant coating forming step, the such surfacetreatments as a surface roughening treatment are not performed and thecorrosion resistant coating 5 is formed by applying the above-describedpaint-like material having affinity with respect to the substrate 3 anddrying the applied paint-like material. The method of applying thecorrosion resistant paint-like material is preferably to roll it onusing a roll coater, but it is also acceptable to use such paintapplication methods as spraying painting, dipping, and wash-coating. Onemethod of drying the corrosion resistant paint-like material when thepaint-like material is applied with a roller is to transport thesubstrate 3 through a drying furnace located downstream of the roller,but the invention is not limited to this method. Specifically, thedrying is preferably conducted in an atmosphere having a temperature ofat least 180° C. and not more than 300° C. for 10 minutes or less.During the drying process, the hydrophilic groups contained in theemulsifying agent and other components of the corrosion resistantpaint-like material change into other functional groups and disappear.

In the hydrophilic coating forming step, the hydrophilic coating 7 isformed by applying the above-described hydrophilic paint-like materialto the surface of the corrosion resistant coating 5 and drying theapplied paint-like material. The methods of applying and drying thehydrophilic paint-like material can be the same as those describedregarding the corrosion resistant coating forming step, but it is alsoacceptable for different methods to be used. In the case of thehydrophilic paint-like material, the drying is preferably conducted inan atmosphere having a temperature of at least 150° C. and not more than250° C. for 10 minutes or less.

With this manufacturing method, since the paint-like material used toform the corrosion resistant coating 5 contains a prescribed content(weight percentage) of an alcohol-based solvent and thus the surfacetension thereof is small, the paint-like material has good attractionwith respect to the substrate 3 even though the substrate has not beensubjected to a roughening treatment. As a result, the paint-likematerial has excellent adhesion with respect to the substrate 3 when itis in the form of a coating. Thus, a plate material 1 having excellentdurability can be obtained with a simple method.

Additionally, the production cost of the plate material 1 can be reducedbecause such surface treatments as oil removal treatments and rougheningtreatments can be omitted, thereby reducing the number of manufacturingsteps and eliminating the need for the processing equipment that wouldotherwise be required for said surface treatments. In particular, sincethe substrate 3 does not need to be subjected to a chromic acidtreatment, the production cost can be reduced because there is no needto prepare a treatment layer for the chromic acid treatment and theprocess is environmentally friendly because there is no discharge ofwaste liquid containing heavy metals.

Additionally, although the corrosion resistant coating 5 is formeddirectly on the surface of the substrate 3 without a chromate coatingdisposed there-between, the plate material 1 obtained with this methodhas excellent corrosion resistance because the corrosion resistantcoating 5 is made of a hydrophobic organic compound and the decline incorrosion resistance that would otherwise result from the omission ofthe chromate coating is suppressed.

Also, with this manufacturing method, since both a corrosion resistantcoating 5 and a hydrophilic coating 7 are formed, the properties of bothcorrosion resistance and hydrophilicity are obtained. Since thecorrosion resistant coating 5 is made of a hydrophobic organic compound,erosion of the corrosion resistant coating by adhered water is almosteliminated in comparison with a corrosion resistant coating made of awater soluble resin and, thus, moisture is prevented from penetratingthe corrosion resistant coating 5 and causing corrosion to start andprogress between the substrate 3 and the corrosion resistant coating 5.In short, a plate material 1 having excellent durability can be obtainedwith this method.

Since the plate material 1 has a high corrosion resistance and itssurface is highly hydrophilic, it is well suited for use as a heatexchanger heat radiating fin 11 like that shown in FIGS. 2 and 3,particularly a heat radiating fin 11 for a heat exchange used in anoutdoor unit. The heat radiating fin 11 is made, for example, bypunching the plate material 1 with a prescribed die.

(a) It is acceptable for the hydrophilic paint-like material used toform the hydrophilic coating to contain an organic solvent in additionto the components mentioned in the previously described embodiment.There are no particular limitations on organic solvent so long as it isvolatile, but ammonia and alcohol-based solvents are preferred. From theviewpoint of flammability and legal constraints, the content of theorganic solvent in the hydrophilic paint-like material is preferably inthe range of 5 to 20 wt % (i.e., 5 to 20 weight units of organic solventper 100 weight units of hydrophilic paint-like material).

Also, there does not necessarily have to be a well defined boundarysurface between the corrosion resistant coating and the hydrophiliccoating. It is acceptable for the organic solvent of the hydrophilicpaint-like material to chemically affect the surface of the corrosionresistant coating (for example, forming roughness on the surface) suchthat the two coatings are closely adhered to each other and a portion ofthe constituent components of the corrosion resistant coating aredispersed in the hydrophilic coating when coatings are formed.

Research conducted by the inventor demonstrates that a plate materialprovided with such a hydrophilic coating has a small contact angle(i.e., less than 30°) in the initial state. Here, “initial state” refersto the state of the plate material in the period from when thehydrophilic coating 7 is formed until when the plate material is firstused.

Since the hydrophilic paint-like material contains an organic solvent,it affects the surface of the corrosion resistant coating when it isapplied to the surface of the corrosion resistant coating. As a result,the corrosion resistant coating and the hydrophilic coating of the platematerial have increased adhesion at the boundary surface there-between.Thus, with this method, the hydrophilic coating can be formedsatisfactorily on the surface of the corrosion resistant coating using asimple method that does not involve such special surface treatments as acorona discharge treatment.

(b) It is also acceptable to manufacture a plate material like thatdescribed in (a) above, wherein a corona discharge or other plasmatreatment or an ultraviolet irradiation treatment is applied to thesurface of the corrosion resistant coating instead of adding an organicsolvent to the hydrophilic paint-like material. A hydrophilic paint-likematerial that does not contain an organic solvent (although it isacceptable if it does contain an organic solvent) is then applied to thecorrosion resistant coating.

(c) It is acceptable if an oil removal treatment is applied to thesurface of the substrate in the substrate preparation step.

(d) It is not necessary for the substrate to be made of pure aluminiumor an aluminium alloy.

With the present invention, excellent adhesion is achieved between thecoating and the substrate even when the substrate has not been roughenedbecause the coating is made with paint-like material having affinitywith respect to the substrate. Since this plate material can be obtainedwithout applying a roughening treatment, the production cost is reduced.

With the present invention, the adhesion between the substrate and thecoating is improved and the cost required to produce the plate materialis reduced. Furthermore, since the corrosion resistant coating is madeof a hydrophobic organic compound and does not contain a hydrophilicgroup, erosion of the corrosion resistant coating by adhered water issuppressed in comparison with a corrosion resistant coating made of awater soluble resin and moisture can be prevented from penetrating thecorrosion resistant coating and causing the substrate to corrode.

1. A plate material, comprising: a plate substrate being free ofprotrusions and depressions of submicron order oriented in a thicknessdirection thereof with a rolling oil being used and remaining on theplate substrate; a substrate coating formed on a surface of the platesubstrate with a corrosion resistant hydrophobic organic paint material,the corrosion resistant hydrophobic organic paint material including acoating film component, the coating film component being a two-componentresin, and an alcohol-based solvent, a content of the alcohol-basedsolvent being 1 to 10 wt % when the corrosion resistant hydrophobicorganic paint material is applied; and a hydrophilic coating made of ahydrophilic paint material being provided on a surface of the substratecoating, the corrosion resistant hydrophobic organic paint materialhaving affinity with both the plate substrate with the rolling oilremaining on the surface and the hydrophilic coating.
 2. The platematerial recited in claim 1, wherein the paint material includes ahydrophobic organic paint material.
 3. The plate material recited inclaim 1, wherein a surface tension of the paint material is equal to orgreater than 25 and less than or equal to 35 dyn/cm.
 4. The platematerial recited in claim 1, wherein the paint material contains analcohol-based solvent at a content of 1 to 5 wt %.
 5. The plate materialrecited in claim 1, wherein the alcohol-based solvent is madesubstantially of an alcohol having four or more carbon atoms.
 6. Theplate material recited in claim 1, wherein the viscosity of the paintmaterial is equal to or greater than 5 Pa-s and less than or equal to 20Pa-s.
 7. The plate material recited in claim 1, wherein the hydrophilicpaint material contains a volatile organic solvent.
 8. A plate materialrecited in claim 1, wherein the surface of the substrate having thesubstrate coating has not been subjected to a chromic acid treatment. 9.The plate material recited in claim 1, wherein the surface of thesubstrate having the substrate coating has not been subjected to an oilremoval treatment.
 10. The plate material recited in claim 1, whereinthe substrate is made of pure aluminum or an aluminum alloy.
 11. A heatradiating fin of a heat exchanger including a plate material as recitedin claim
 1. 12. A plate material manufacturing method, comprising:preparing a plate substrate being free of protrusions and depressions ofsubmicron order oriented in a thickness direction thereof and having arolling oil on a surface of the plate substrate; applying a corrosionresistant hydrophobic organic paint material on the rolling oil which ison the surface of the plate substrate for forming a substrate coating,the corrosion resistant hydrophobic organic paint material including acoating film component, the coating film component being a two-componentresin, and an alcohol-based solvent, a content of the alcohol-basedsolvent being 1 to 10 wt % when the corrosion resistant hydrophobicorganic paint material is applied; and providing a hydrophilic coatingon a surface of the substrate coating by applying a hydrophilic paintmaterial, the corrosion resistant hydrophobic organic paint materialhaving affinity with both the plate substrate with the rolling oilremaining on the surface and the hydrophilic coating.
 13. The platematerial manufacturing method recited in claim 12, wherein the paintmaterial is a hydrophobic organic paint material.
 14. The plate materialmanufacturing method recited in claim 12, wherein the paint material hasa surface tension of 25 dyn/cm to 35 dyn/cm.
 15. The plate materialmanufacturing method recited in claim 12, wherein the paint materialcontains an alcohol-based solvent at a content of 1 to 5 wt %.
 16. Theplate material manufacturing method recited in claim 12, wherein thealcohol-based solvent is made substantially of an alcohol having four ormore carbon atoms.
 17. The plate material manufacturing method recitedin claim 12, wherein the viscosity of the paint material is equal to orgreater than 5 Pa-s and less than or equal to 20 Pa-s. Zone Name:OCRZone
 18. The plate material manufacturing method recited in claim 12,wherein the hydrophilic paint material contains a volatile organicsolvent.
 19. The plate material manufacturing method recited in claim12, wherein the corrosion resistant paint material is applied on thesubstrate that has not been subjected to a chromic acid treatment. 20.The plate material manufacturing method recited in claim 12, wherein thecorrosion resistant paint material is applied on the substrate that hasnot been subjected to an oil removal treatment.
 21. The plate materialmanufacturing method recited in claim 12, wherein the substrate is madeof pure aluminum or an aluminum alloy.
 22. The plate materialmanufacturing method recited in claim 12, further comprising forming theplate material into a heat radiating fin of a heat exchanger.
 23. Theplate material recited in claim 1, wherein the substrate coating isformed after drying the corrosion resistant hydrophobic organic paintmaterial that contains the alcohol-based solvent.
 24. The plate materialmanufacturing method recited in claim 12, further comprising drying thecorrosion resistant hydrophobic organic paint material for forming thesubstrate coating.